eap.c

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/*
 * Copyright (C) 2021 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <byteswap.h>
#include <ipxe/netdevice.h>
#include <ipxe/eap.h>

/** @file
 *
 * Extensible Authentication Protocol
 *
 */

/**
 * Transmit EAP response
 *
 * @v supplicant        EAP supplicant
 * @v rsp               Response type data
 * @v rsp_len           Length of response type data
 * @ret rc              Return status code
 */
int eap_tx_response ( struct eap_supplicant *supplicant,
                      const void *rsp, size_t rsp_len ) {
        struct net_device *netdev = supplicant->netdev;
        struct eap_message *msg;
        size_t len;
        int rc;

        /* Allocate and populate response */
        len = ( sizeof ( *msg ) + rsp_len );
        msg = malloc ( len );
        if ( ! msg ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        msg->hdr.code = EAP_CODE_RESPONSE;
        msg->hdr.id = supplicant->id;
        msg->hdr.len = htons ( len );
        msg->type = supplicant->type;
        memcpy ( msg->data, rsp, rsp_len );
        DBGC ( netdev, "EAP %s Response id %#02x type %d\n",
               netdev->name, msg->hdr.id, msg->type );

        /* Transmit response */
        if ( ( rc = supplicant->tx ( supplicant, msg, len ) ) != 0 ) {
                DBGC ( netdev, "EAP %s could not transmit: %s\n",
                       netdev->name, strerror ( rc ) );
                goto err_tx;
        }

 err_tx:
        free ( msg );
 err_alloc:
        return rc;
}

/**
 * Transmit EAP NAK
 *
 * @v supplicant        EAP supplicant
 * @ret rc              Return status code
 */
static int eap_tx_nak ( struct eap_supplicant *supplicant ) {
        struct net_device *netdev = supplicant->netdev;
        unsigned int max = table_num_entries ( EAP_METHODS );
        uint8_t methods[ max + 1 /* potential EAP_TYPE_NONE */ ];
        unsigned int count = 0;
        struct eap_method *method;

        /* Populate methods list */
        DBGC ( netdev, "EAP %s Nak offering types {", netdev->name );
        for_each_table_entry ( method, EAP_METHODS ) {
                if ( method->type > EAP_TYPE_NAK ) {
                        DBGC ( netdev, "%s%d",
                               ( count ? ", " : "" ), method->type );
                        methods[count++] = method->type;
                }
        }
        if ( ! count )
                methods[count++] = EAP_TYPE_NONE;
        DBGC ( netdev, "}\n" );
        assert ( count <= max );

        /* Transmit response */
        supplicant->type = EAP_TYPE_NAK;
        return eap_tx_response ( supplicant, methods, count );
}

/**
 * Handle EAP Request-Identity
 *
 * @v supplicant        EAP supplicant
 * @v req               Request type data
 * @v req_len           Length of request type data
 * @ret rc              Return status code
 */
static int eap_rx_identity ( struct eap_supplicant *supplicant,
                             const void *req, size_t req_len ) {
        struct net_device *netdev = supplicant->netdev;
        void *rsp;
        int rsp_len;
        int rc;

        /* Treat Request-Identity as blocking the link */
        DBGC ( netdev, "EAP %s Request-Identity blocking link\n",
               netdev->name );
        DBGC_HDA ( netdev, 0, req, req_len );
        netdev_link_block ( netdev, EAP_BLOCK_TIMEOUT );

        /* Mark EAP as in progress */
        supplicant->flags |= EAP_FL_ONGOING;

        /* Construct response, if applicable */
        rsp_len = fetch_raw_setting_copy ( netdev_settings ( netdev ),
                                           &username_setting, &rsp );
        if ( rsp_len < 0 ) {
                /* We have no identity to offer, so wait until the
                 * switch times out and switches to MAC Authentication
                 * Bypass (MAB).
                 */
                DBGC2 ( netdev, "EAP %s has no identity\n", netdev->name );
                supplicant->flags |= EAP_FL_PASSIVE;
                rc = 0;
                goto no_response;
        }

        /* Transmit response */
        if ( ( rc = eap_tx_response ( supplicant, rsp, rsp_len ) ) != 0 )
                goto err_tx;

 err_tx:
        free ( rsp );
 no_response:
        return rc;
}

/** EAP Request-Identity method */
struct eap_method eap_identity_method __eap_method = {
        .type = EAP_TYPE_IDENTITY,
        .rx = eap_rx_identity,
};

/**
 * Handle EAP Request
 *
 * @v supplicant        EAP supplicant
 * @v msg               EAP request
 * @v len               Length of EAP request
 * @ret rc              Return status code
 */
static int eap_rx_request ( struct eap_supplicant *supplicant,
                            const struct eap_message *msg, size_t len ) {
        struct net_device *netdev = supplicant->netdev;
        struct eap_method *method;
        const void *req;
        size_t req_len;

        /* Sanity checks */
        if ( len < sizeof ( *msg ) ) {
                DBGC ( netdev, "EAP %s underlength request:\n", netdev->name );
                DBGC_HDA ( netdev, 0, msg, len );
                return -EINVAL;
        }
        if ( len < ntohs ( msg->hdr.len ) ) {
                DBGC ( netdev, "EAP %s truncated request:\n", netdev->name );
                DBGC_HDA ( netdev, 0, msg, len );
                return -EINVAL;
        }
        req = msg->data;
        req_len = ( ntohs ( msg->hdr.len ) - sizeof ( *msg ) );

        /* Record request details */
        supplicant->id = msg->hdr.id;
        supplicant->type = msg->type;
        DBGC ( netdev, "EAP %s Request id %#02x type %d\n",
               netdev->name, msg->hdr.id, msg->type );

        /* Handle according to type */
        for_each_table_entry ( method, EAP_METHODS ) {
                if ( msg->type == method->type )
                        return method->rx ( supplicant, req, req_len );
        }
        DBGC ( netdev, "EAP %s requested type %d unknown:\n",
               netdev->name, msg->type );
        DBGC_HDA ( netdev, 0, msg, len );

        /* Send NAK if applicable */
        if ( msg->type > EAP_TYPE_NAK )
                return eap_tx_nak ( supplicant );

        return -ENOTSUP;
}

/**
 * Handle EAP Success
 *
 * @v supplicant        EAP supplicant
 * @ret rc              Return status code
 */
static int eap_rx_success ( struct eap_supplicant *supplicant ) {
        struct net_device *netdev = supplicant->netdev;

        /* Mark authentication as complete */
        supplicant->flags = EAP_FL_PASSIVE;

        /* Mark link as unblocked */
        DBGC ( netdev, "EAP %s Success\n", netdev->name );
        netdev_link_unblock ( netdev );

        return 0;
}

/**
 * Handle EAP Failure
 *
 * @v supplicant        EAP supplicant
 * @ret rc              Return status code
 */
static int eap_rx_failure ( struct eap_supplicant *supplicant ) {
        struct net_device *netdev = supplicant->netdev;

        /* Mark authentication as complete */
        supplicant->flags = EAP_FL_PASSIVE;

        /* Record error */
        DBGC ( netdev, "EAP %s Failure\n", netdev->name );
        return -EPERM;
}

/**
 * Handle EAP packet
 *
 * @v supplicant        EAP supplicant
 * @v data              EAP packet
 * @v len               Length of EAP packet
 * @ret rc              Return status code
 */
int eap_rx ( struct eap_supplicant *supplicant, const void *data,
             size_t len ) {
        struct net_device *netdev = supplicant->netdev;
        const union eap_packet *eap = data;

        /* Sanity check */
        if ( len < sizeof ( eap->hdr ) ) {
                DBGC ( netdev, "EAP %s underlength header:\n", netdev->name );
                DBGC_HDA ( netdev, 0, eap, len );
                return -EINVAL;
        }

        /* Handle according to code */
        switch ( eap->hdr.code ) {
        case EAP_CODE_REQUEST:
                return eap_rx_request ( supplicant, &eap->msg, len );
        case EAP_CODE_RESPONSE:
                DBGC2 ( netdev, "EAP %s ignoring response\n", netdev->name );
                return 0;
        case EAP_CODE_SUCCESS:
                return eap_rx_success ( supplicant );
        case EAP_CODE_FAILURE:
                return eap_rx_failure ( supplicant );
        default:
                DBGC ( netdev, "EAP %s unsupported code %d\n",
                       netdev->name, eap->hdr.code );
                DBGC_HDA ( netdev, 0, eap, len );
                return -ENOTSUP;
        }
}

/* Drag in objects via eap_rx() */
REQUIRING_SYMBOL ( eap_rx );

/* Drag in EAP configuration */
REQUIRE_OBJECT ( config_eap );